1. Field of the Invention
The invention relates to a lens array and a display, and particularly relates to a zoom lens array and a switchable two and three dimensional display.
2. Description of Related Art
As display technology advances, displays have been developed from displaying a two dimensional image to displaying a three dimensional image. FIG. 1 is a schematic view of a lenticular lens array of a conventional three dimensional image display. Referring to FIG. 1, a lenticular lens array 100 is formed by a plurality of lenticular lenses 100A. An incident light L1 which passes through each of the lenticular lenses 100A is focused by the lenticular lenses 100A and forms an emitting light L2 proceeding along a left direction and a right direction. That is, the lenticular lens array 100 is capable of projecting the light of an image respectively to the left and right eyes of a viewer, so as to achieve three dimensional effects.
However, it is fairly difficult to fabricate the lenticular lenses 100A, and it costs a lot to reach the predetermined optical precision. In addition, the focal length of the lenticular lenses 100A is fixed and cannot be changed after the fabrication. The viewer can see three dimensional images only in a certain distance, which imposes a limitation to the use of the three dimensional image display.
FIG. 2 is a schematic view of a conventional liquid crystal zoom lens. As shown in FIG. 2, the liquid crystal zoom lens 200 includes a bottom glass substrate 210, a bottom electrode 220, a spacer 230, a liquid crystal layer 240, a top glass substrate 250, and a top electrode 260.
The positions of the foregoing elements are shown in FIG. 2, wherein the bottom electrode 220 is disposed on the bottom glass substrate 210. The spacer 230 is disposed on the bottom electrode 220. The top glass substrate 250 is disposed on the spacer 230. The liquid crystal layer 240 is located between the bottom electrode 220 and the top glass substrate 250. The top electrode 260 is disposed on the top glass substrate 250 and positioned at two ends of the top glass substrate 250.
It is noted that the top electrode 260 is a strip electrode and the bottom electrode 220 is a planar electrode. Such a configuration of electrodes can generate a non-uniform electric field distribution E in the liquid crystal layer 240. The non-uniform electric field distribution E varies the deflection (phase retardation) of the liquid crystal molecules (not shown) in different areas of the liquid crystal layer 240. A light (not shown) passing through a central part of the liquid crystal zoom lens 200 is faster than a light passing through a peripheral part of the liquid crystal zoom lens 200, resulting in focusing effect.
To generate a favorable focusing effect, the top glass substrate 250 which has a certain thickness needs to be disposed between the top electrode 260 and the liquid crystal layer 240. More specifically, because of the top glass substrate 250, a sufficient distance is maintained between the top electrode 260 and the bottom electrode 220 to gradually vary the electric field and generate the non-uniform electric field distribution E as shown in FIG. 2. Without the top glass substrate 250, the bottom electrode 220 and the top electrode 260 on both sides would be too close to each other. Consequently, electric field would be concentrated on two sides of the liquid crystal zoom lens 200, and the non-uniform electric field distribution E would not be formed. However, since it is required to dispose the top glass substrate 250, the thickness of the liquid crystal zoom lens 200 is increased and the structure of the liquid crystal zoom lens 200 is complicated. Moreover, the fabrication processes of the liquid crystal zoom lens 200 become more complex, which increases the production costs.